We follow after previous work  [1]} and employ a Slater-Jastrow trial wavefunction of the form \(\Psi _\mathrm {T}= \mathrm {e}^{-J}\det [\phi (\mathbf {s}_{i,j})]\) . The determinant ensures the correct fermionic spin-symmetry. The pairing orbital \(\phi (\mathbf {s}_{i,j})\)  comprises plane wave and polynomial expansions in the fermion separations \(\mathbf {s}_{i,j}\) . The plane wave part of the pairing wavefunction equals the exact Hartree-Fock ground state wavefunction for the non-interacting fermion gas, and in the presence of attractive interactions, the polynomial component of the pairing orbital can shift the nodal surface to smoothly transform to a superconducting wavefunction. To capture additional fermion correlations, we include the Jastrow factor \(J\)  which is a function of all opposite-spin fermion separations comprising a short range isotropic \(u\)  term, anisotropic \(p\)  terms [2]}, and a \(\nu \)  term [3]} that reflects the simulation cell symmetry.
